The extent of regeneraion of the tissues comprising the arterial wall will be determinedin the dog and the rabbit models. Factors influencing the regeneration of these cell types will be modified to alter the regenerative response to the prosthetic replacement of arterial segments. These modifying factors include absorbable and partially absorbable compound prostheses of high porosity and low tissue reactivity, alterations in graft design and the application of endothelial cell transplantation into the prostheses. The regenerative response to these modifying factors will e studied in vessels of several dimensions employing light and electron microscopic techniques, immunohistologic methodologies and determinations of bursting strengths of the regenerated vessels and their resistance to thrombosis and infection. The effect of these factors on degenerative changes consistent with early atherogenesis will be examined. The long range goal is the application of methods of enhancing and controlling arterial regeneration over absorbable scaffolds inte replacement of diseased small and medium caliber arteries in man, areas in which the conventional techniques of arterial replacement have yielded relatively poor long term results.